Is Sikhism a cross between Hinduism and Islam?  

No, Sikhism is different from both Islam and Hinduism, and has been interpreted wrongly as being a cross between Hinduism and Islam. Guru Nanak was born in a Hindu family, and yet he refused to follow the dictates of his own family tradition. He revealed his own unique teachings. Sikhism is an independent spiritual path with its own precepts, social principles and organization.  

Why do people carry the kirpan and what is it used for?   

A kirpan is a small sickle-shaped sword and it is an article of faith for an initiated Sikh who chooses to take a vow to follow Sikh principles more closely. It symbolizes one’s commitment to justice for all. It represents divine power and it is never used as a weapon.